Normally, when a system integration service or system-outsourcing service is provided, service level agreements are reached between service provider and client. Therefore, the achievement of service levels needs to be measured. To work out service levels concerning system response time, it is necessary to measure and evaluate response times in the system development and testing phases, and continue to measure and evaluate them after the system starts production runs. This requires an objective system for measuring response times.
In the case of Web application systems and client/server systems, the source location of a user request and the destination location of a response to the user are the same. In such cases, a system that generates requests and receives responses can measure the time interval between the generation of a request and approval of a response using its system clock.
Clearly, the above mentioned technique used when the source location of a request and the destination location of a response are the same cannot be applied to cases where the source location of a request and the destination location of a response are different.
If the source location of a request and the destination location of a response are different, the response time can be measured, for example, as follows by using synchronization with a server that provides standard time. Specifically, the system from which the request is issued and the system at which the response arrives access the server that provides standard time and synchronize their system clocks with the standard time. The time when the request was issued and the time when the response was received are stamped according to the system clocks of the respective systems. Later, these times are gathered at one location to calculate the response time.
The above mentioned technique for synchronizing system clocks using standard time does not pose a particular problem if the temporal accuracy required is within a few seconds. However, difficulties arise if a subsecond temporal accuracy is required. Synchronization techniques on the order of several hundred milliseconds have been established on the Internet, but overhead information is necessary for synchronization. In the case of systems that require fast response, this overhead cannot be ignored as a load. Also, it is difficult to synchronize system clocks properly. Particularly, large systems such as systems for Olympic games, which require fast response speeds (one second or less) and consist of a large number of devices have difficulty in synchronizing the devices properly.
An object of the present invention is to provide a technique for measuring response times, for example, at one second resolution or better when the starting location (start device) and ending location (end device) of processing are different.